Multitone radiation is a promising technique to mitigate stimulated Brillouin scattering effects in narrow-linewidth fiber amplifiers. We demonstrate coherent beam combination of three two-tone fiber amplifiers using a stochastic parallel gradient descent (SPGD) algorithm. Phase control on the fiber amplifiers are performed by running the SPGD algorithm on a digital signal processor. The contrast of far-field intensity pattern of a coherently combined beam is more than 85%. Experimental results validate that a single-frequency seed laser is not indispensable for coherent beam combination in master oscillator power amplifier configuration.
© 2009 Optical Society of America
Lasers and Laser Optics
Original Manuscript: July 30, 2009
Manuscript Accepted: August 18, 2009
Published: September 23, 2009
Pu Zhou, Yanxing Ma, Xiaolin Wang, Haotong Ma, Xiaojun Xu, and Zejin Liu, "Coherent beam combination of three two-tone fiber amplifiers using stochastic parallel gradient descent algorithm," Opt. Lett. 34, 2939-2941 (2009)